When you open Control Panel, you receive a message similar to:
Windows cannot find C:\Windows\Rundll32.exe, make sure you typed the name correctly and try again.
You may have a virus or Rundll32.exe is damaged or missing.
To restore a clean version of Rundll32.exe:
1. Mount the Windows XP CD-ROM.
2. Open a CMD.exe session.
3. Type expand <CD-ROM:>\i386\rundll32.ex_ %Systemroot%\rundll32.exe and press Enter.
4. Shutdown and restart Windows XP.